The present invention relates to a fuel injection timing control unit for an electronic controlled fuel injection apparatus mounted on an internal combustion engine, and more particularly to a fuel injection timing control unit which enables a fuel injection timing to be adjustable.
In the electronic controlled fuel injection systems, there have been known three different types. One of the types is such an electronic controlled fuel injection system as a fuel is injected at the same time to all the cylinders of an engine. Another of the types is such an electronic controlled fuel injection system as a fuel is injected to a group of cylinders. The other of the types is such an electronic controlled fuel injection system as a fuel is separately injected to each of the cylinders in the condition that the fuel injection timing is synchronized with the induction stroke of each cylinder. According to the foregoing three types of an electronic controlled fuel injection systems, all the timing of injecting a fuel into a cylinder or cylinders is fixed. As the fuel injection timing is fixed, this impairs the response to an operator's demand that the acceleration of a vehicle is necessitated, in the transitional engine running condition. For example, in the engine running condition that a quick acceleration of a vehicle is necessitated. To obviate the foregoing drawback, the following two countermeasures are proposed. The first is, fuel is injected into the cylinders in the condition that the fuel injection timing is not synchronized with the induction stroke of the cylinders. The second is, an additional amount of a fuel is injected to the cylinders when the quick acceleration of a vehicle is necessitated. These countermeasures necessitate a complicated control. Further, the additional amount of a fuel to be injected is limited in order to reduce the amount of the exhaust gas, especially the components of HO and CO, discharged into the atmosphere. Hence, it is desirable to reduce the additional amount of injected fuel to be as little as possible.